Wireless Lan Error Correction

Archived from groups: alt.internet.wireless (More info?)

Hi,


My wireless setup is :

NetGear WGT634u 108 mbps wireless router with 4 10/100 ethernet ports

Netgear WG511T 108 mbps PCMCIA wireless network card

I use these for playing games on the lan and surfing the net.

Ive never had any problems with quake3 operation flashpoint on the
lan.

However while downloading from the internet across the wireless
network it always fails after a few miutes (randomly). Also if i try
and play a snooker game against someone on the internet it fails after
a random period too.

I assume error correction is the problem.
I have an excellent signal strength on the laptop.


Any ideas ?


Damo784
4 answers Last reply
More about wireless error correction
  1. Archived from groups: alt.internet.wireless (More info?)

    On 20 Aug 2004 04:55:03 -0700, damienfitzgerald@vodafone.ie (Damo784)
    wrote:

    >My wireless setup is :
    >NetGear WGT634u 108 mbps wireless router with 4 10/100 ethernet ports
    >Netgear WG511T 108 mbps PCMCIA wireless network card
    >I use these for playing games on the lan and surfing the net.
    >Ive never had any problems with quake3 operation flashpoint on the
    >lan.
    >
    >However while downloading from the internet across the wireless
    >network it always fails after a few miutes (randomly). Also if i try
    >and play a snooker game against someone on the internet it fails after
    >a random period too.
    >
    >I assume error correction is the problem.
    >I have an excellent signal strength on the laptop.

    Assumption, the mother of all screwups.

    There is no error correction. There is error detection and resend the
    packets at the TCP level. However that only works with TCP, not UDP
    which does not require an acknowledgement. If your online games are
    UDP or multicast, there is no resend. If something causes your
    wireless device to lose connection long enough for a timeout, it just
    gives up.

    The two times I troubleshot one of these "random" errors, I traced it
    down to RF interference. The first was from a neighbors microwave
    oven. The 2nd was from a cordless phone. Look in the log file on the
    router to see if there are any clues as to timing and signal loss. I
    would normally suggest a complicated method of interference detection
    using directional antennas and a spectrum analyzer. However, both of
    these were discovered with simple observation.

    Speaking of interference, I'm suppose to troubleshoot wireless
    "connectivity problems" in the cafeteria area of an office building
    where about 6ea microwave ovens operate almost continuously during
    lunch time. People are complaining that they can't reliably use the
    corporate wireless network in the cafeteria. They already suspect the
    microwave ovens but want to know if I can do something about it.
    Maybe some of that WiFi absorbent wallpaper. Sigh.


    --
    Jeff Liebermann jeffl@comix.santa-cruz.ca.us
    150 Felker St #D http://www.LearnByDestroying.com
    Santa Cruz CA 95060 AE6KS 831-336-2558
  2. Archived from groups: alt.internet.wireless (More info?)

    "Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
    news:l36ci094a29l91il4l0js46jag08je9cn8@4ax.com...
    [snip]

    > Speaking of interference, I'm suppose to troubleshoot wireless
    > "connectivity problems" in the cafeteria area of an office building
    > where about 6ea microwave ovens operate almost continuously during
    > lunch time. People are complaining that they can't reliably use the
    > corporate wireless network in the cafeteria. They already suspect the
    > microwave ovens but want to know if I can do something about it.
    > Maybe some of that WiFi absorbent wallpaper. Sigh.

    Jeff,

    You're not far off: at building I worked in once, we wound up constructing a
    Faraday Cage around the microwaves in the cafeteria, and it was very
    effective at eliminating stray radiation into the eating area.

    This was a bit before WiFi: they were concerned about possible interference
    with cardiac pacemakers.

    William
  3. Archived from groups: alt.internet.wireless (More info?)

    <<<<<<<<<<<There is no error correction. There is error detection and
    resend the
    packets at the TCP level. However that only works with TCP, not UDP
    which does not require an acknowledgement. If your online games are
    UDP or multicast, there is no resend. If something causes your
    wireless device to lose connection long enough for a timeout, it just
    gives up>>>>>>>>>>>>>


    This is very interesting.

    I have 2 questions

    1) When downloading an application does it use tcp?
    Because as i said the download keeps stooping after a few minutes.

    2) Is there not any sotware that i could install at the pc (Gateway to
    the internet ) that is physically connected to the router and also
    software that would be installed on the wireless laptop that would
    monitor data that was sent to it?

    So say for example between these two it would use its own tcp protocol
    (even if the snooker game was using udp )and could there for request
    the gateway pc to resend the data.

    Damo784
  4. Archived from groups: alt.internet.wireless (More info?)

    On 20 Aug 2004 16:14:45 -0700, damienfitzgerald@vodafone.ie (Damo784)
    wrote:

    ><<<<<<<<<<<There is no error correction. There is error detection and
    >resend the
    >packets at the TCP level. However that only works with TCP, not UDP
    >which does not require an acknowledgement. If your online games are
    >UDP or multicast, there is no resend. If something causes your
    >wireless device to lose connection long enough for a timeout, it just
    >gives up>>>>>>>>>>>>>

    >1) When downloading an application does it use tcp?
    >Because as i said the download keeps stooping after a few minutes.

    HTTP and ftp downloads both use TCP. Streaming audio, VoIP, and
    anything that's time sensitive, uses UDP. You can get a good idea of
    which protocols use which flavour by looking in the file:
    c:\windoze\services
    The full list is at:
    http://www.iana.org/assignments/port-numbers
    Just search for your favorite application.

    If you're downloading using a web browser or ftp client, it most
    assuredly uses TCP. That means the server demands ACK's before
    continueing to spew packets in your direction. For most systems
    (except Satellite ISP's), the server will send 64Kbytes worth of
    packets before it waits for ACK's.

    To insure maximum confusion, many protocols use both TCP and UDP. In
    general, UDP is used for the time sensitive streaming, while TCP is
    used as a control channel.

    What usually happens is that your wireless link goes dead for a while
    thanks to interference. Eventually, it recovers and the download
    continues. However, if the interruption is too long, the server will
    timeout and stop sending. There are protocols that work around this
    effect (Bittorrent, FastTrack, P2Pism, and various peer-to-peer
    protocols). However, if you're getting a "connection reset by peer"
    message, your connection was lost. Incidentally, traffic doesn't need
    to totally stop to generate a reset. I merely needs to have a high
    enough packet loss that an excessive number of resends are generated.

    >2) Is there not any sotware that i could install at the pc (Gateway to
    >the internet ) that is physically connected to the router and also
    >software that would be installed on the wireless laptop that would
    >monitor data that was sent to it?

    Sure. SNMP will disclose both the type of errors and keep a count.
    MRTG will display a pretty graph of the damage. Ideally, you would
    want an access point and client radio that both can do SNMP. Few of
    the cheap radios have SNMP and the few that do (DLink DWL-900AP+)
    don't have MIB's to decode the garbage. Most Lucent/Orinocco/Proxim
    hardware does have a nice SNMP stack.

    See:

    http://groups.google.com/groups?selm=85nih0d5oem1s6lbqg4lu3b563kejtucr4%404ax.com
    for some drivel I posted on the subject.

    There are other stand alone utilities that basically do the same thing
    on the PC. However, these will not show errors at the MAC (radio)
    level as SNMP will.

    >So say for example between these two it would use its own tcp protocol
    >(even if the snooker game was using udp )and could there for request
    >the gateway pc to resend the data.

    I have no idea what your game runs. When your game is running, open
    an MSDOS window on your computah:
    Run -> cmd (W2K and XP)
    Run -> command (W95/98/ME)
    and run:
    netstat -n (protocols and ports used by IP address)
    netstat (same but with DNS names)
    netstat -e (errors)
    The protocol (TCP/UDP/ICMP) is in the "Proto" column.

    However, fixing an what I'm *GUESSING* is an interference problem by
    messing with the protocol pile is not my idea of the right way to do
    things. Try to find out why the downloads stop, and work on fixing
    the problem at the source. Then, if that fails, do the protocol
    exercises.


    --
    # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
    # 831.336.2558 voice http://www.LearnByDestroying.com
    # jeffl@comix.santa-cruz.ca.us
    # 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
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